View8 is a static analysis tool designed to decompile serialized V8 bytecode objects (JSC files) into high-level readable code. To parse and disassemble these serialized objects, View8 utilizes a patched compiled V8 binary. As a result, View8 produces a textual output similar to JavaScript.

• Python 3.x
• Disassembler binary. Available versions:
• V8 Version 9.4.146.24 (Used in Node V16.x)
• V8 Version 10.2.154.26 (Used in Node V18.x)
• V8 Version 11.3.244.8 (Used in Node V20.x)

For compiled versions, visit the releases page.

• input_file: The input file name.
• output_file: The output file name.
• --path, -p: Path to disassembler binary (optional).
• --disassembled, -d: Indicate if the input file is already disassembled (optional).
• --export_format, -e: Specify the export format(s). Options are v8_opcode, translated, and decompiled. Multiple options can be combined (optional, default: decompiled).

To decompile a V8 bytecode file and export the decompiled code:

python view8.py input_file output_file

By default, view8 detects the V8 bytecode version of the input file (using VersionDetector.exe) and automatically searches for a compatible disassembler binary in the Bin folder. This can be changed by specifing a different disassembler binary, use the --path (or -p) option:

python view8.py input_file output_file --path /path/to/disassembler

To skip the disassembling process and provide an already disassembled file as the input, use the --disassembled (or -d) flag:

python view8.py input_file output_file --disassembled

Specify the export format(s) using the --export_format (or -e) option. You can combine multiple formats:

• v8_opcode
• translated
• decompiled

For example, to export both V8 opcodes and decompiled code side by side:

python view8.py input_file output_file -e v8_opcode decompiled

By default, the format used is decompiled.

The V8 bytecode version is stored as a hash at the beginning of the file. Below are the options available for VersionDetector.exe:

• -h: Retrieves a version and returns its hash.
• -d: Retrieves a hash (little-endian) and returns its corresponding version using brute force.
• -f: Retrieves a file and returns its version.

Guide/disassembler/patch based on v8dasm and https://github.com/v8/v8/tree/11.3.244.8.

1. Check out your V8 version: https://v8.dev/docs/source-code

2. Apply the patch:

   git apply v8.patch

3. Create a build configuration:

   ./tools/dev/v8gen.py x64.release

4. Edit the build flags in out.gn/x64.release/args.gn (copied the necessary ones from Node.js):

   dcheck_always_on = false
   is_component_build = false
   is_debug = false
   target_cpu = "x64"
   use_custom_libcxx = false
   v8_monolithic = true
   v8_use_external_startup_data = false
   
   v8_static_library = true
   v8_enable_disassembler = true
   v8_enable_object_print = true
   v8_enable_pointer_compression = false

5. Build the static library:

   ninja -C out.gn/x64.release v8_monolith

6. Compile the disassembler:

   g++ -g -I. -Iinclude v8dasm.cpp -o v8dasm -fno-rtti -lv8_monolith -lv8_libbase -lv8_libplatform -ldl -Lout.gn/x64.release/obj/ -pthread -std=c++17